1. Field of the Invention
Embodiments of the present disclosure relate to the field of duct or chamber systems. More particularly, the present disclosure relates to a system and method for detecting unwanted foreign particles within a duct or air handling system.
2. Discussion of Related Art
In air handling or ventilation systems (HVAC), fans draw fresh outside air into a building, and exhaust stale interior air to the outside. These air handling systems use venting or ducts (i.e. ductwork) to provide an air flow path throughout the building, including to and from heaters and/or air conditioners. To assist in adjusting the volume of air flow, volume control dampers and fans may be used. These dampers and fans can be fitted within the ducts themselves and may be manually or automatically activated.
On occasion, unwanted foreign particles may enter the ductwork of such air handling systems. For example, in the case of a fire, smoke may enter the ductwork. To control the spread of smoke throughout the duct system and subsequently other rooms of the building, smoke dampers may be used which may be automated with the use of a mechanical motor, often referred to as an actuator. For example once smoke is detected by a sensor within the duct, the sensor sends a signal to the actuator to close the smoke damper. A signal may also be sent from the sensor to shut down the fans thereby limiting the spread of smoke through the ducts which would otherwise travel to other rooms or parts of the building. Thus, detectors/sensors may be located throughout the ductwork of a building to detect the presence of smoke which triggers the control of fans and dampers to prevent smoke from traveling or spreading to unwanted areas therein.
FIG. 1 is a functional depiction of a conventional duct sensor 100 used to detect smoke within a duct. The duct sensor 100 includes a sampling tube 110, a smoke sensor 120, and exhaust tube 130. The sampling tube 110 is used to collect the smoke and then to guide the air through the smoke sensor 120. After passing through the smoke sensor 120, the air is then released through the exhaust tube 130. If smoke is detected by the smoke sensor 120, display 140 indicates the detection of smoke by the duct sensor 100. Those of ordinary skill in the art will recognize that the depicted system is highly-simplified for ease of explanation.
FIG. 2 illustrates a cross-sectional view of conventional duct sensor 200 attached to duct 240, the walls of which define duct chamber 240a. Smoke sensor 220 is attached to housing 260 and is located outside of duct 240. Housing 260 is connected to exhaust tube 230 and sampling tube 210. To attach housing 260 to duct 240, two holes 215A and 215B must be formed in a wall of the duct to allow sampling tube 210 and exhaust tube 230 to project into duct chamber 240a respectively. As such, this requires two holes for every duct sensor that is attached to a portion of the ductwork. To prevent room particles from entering the duct system or duct particles from entering the room, gaskets or other means (not shown) must be used to seal the two holes. Thus, there exists a need for a new and improved duct sensor/detector to reduce the number of holes that need to be created in a duct system.
Sampling tube 210 also includes access holes 250 for capturing air that flows through duct 240. To prevent sampling tube 210 from recapturing exhausted smoke from exhaust tube 230, sampling tube 210 must be located upstream of exhaust tube 230. This means that exhaust tube 230 must be positioned downstream of sampling tube 210 when attaching the duct sensor 200 to the duct system. Thus, conventional duct sensor 200 must be properly oriented to allow the duct to funnel air in through sampling tube 210, across sensor 220 via housing 260, and out through exhaust tube 230. Hence, there exists a need for a new and improved duct sensor to eliminate possible orientation errors when installing a duct sensor/detector.
Furthermore, air must be flowing through the duct to allow conventional sensor 220 to sample the air in the duct. Therefore, before a conventional duct sensor 200 can be properly tested to make sure the smoke sensor 220 is operating properly, it must be verified that air is flowing within the duct. Thus, in an effort to properly test the smoke sensor 220 and to make sure air is flowing within the duct, a device may be required to be placed within the duct before testing. This device measures the airflow or differential pressure of the duct to indicate whether or not airflow is present around the sensor 220. Without these additional devices, it may be impossible to know whether the smoke supplied for testing has reached the sensor 220 or if the smoke has traversed through the device that measures differential pressure which may compromise testing. Thus, there exists a need for a new and improved duct sensor/detector to eliminate the need for air flow testing.